Microstructures and Properties of Refractory Metal-Silicide Eutectics

1992 ◽  
Vol 273 ◽  
Author(s):  
B. P. Bewlay ◽  
K-M. Chang ◽  
J. A. Sutliff ◽  
M. R. Jackson
Keyword(s):  
Electron Microscopy ◽  
Gas Turbines ◽  
Metal Silicide ◽  
Cold Crucible ◽  
New Materials ◽  
Directionally Solidified ◽  
Levitation Melting ◽  
Czochralski Crystal Growth ◽  
Transmission Electron ◽  
Eutectic Systems

ABSTRACTNew materials with improved high temperature properties are required for higher efficiency gas turbines. One group of alloys which show promise in this area are the eutectic systems Cr-Cr3Si, Nb-Nb3Si, and V-V3Si. Crystals of these refractory metalsilicide eutectics were directionally solidified using Czochralski crystal growth in conjunction with cold crucible levitation melting. The crystals were examined using scanning electron microscopy and transmission electron microscopy. In the present paper, these systems are examined with respect to the directionally solidified eutectic microstructures, phase equilibria, crystallography and mechanical properties.

Morphological Analysis of Particles in Transmission Electron Microscopy Image Using Image Processing

2013 ◽  
Vol 774-776 ◽  
pp. 1262-1266
Author(s):  
Manop Phankokkruad ◽  
Wacharawichanant Sirirat
Keyword(s):  
Electron Microscopy ◽  
Image Processing ◽  
Transmission Electron Microscopy ◽  
Morphological Analysis ◽  
Transmission Electron Microscopy Image ◽  
Processing Method ◽  
New Materials ◽  
Manual Method ◽  
Transmission Electron ◽  
Microscopy Image

The analysis of material particles in the transmission electron microscopy (TEM) image is the most important in the development and synthesis of the new materials for application in many fields. Manual identification is the hard work, spent a lot of time and inaccurate method. To solve this problem, the image processing is proposed for automatically identifies the material particles boundary and size in TEM images in or order to extract the useful data. The image processing method has been experimented on variety of TEM images and very promising results have been achieved given more accuracy. Experimental results show that the proposed method gave the high adaptability, more accurate and rapidly than the manual method.

Studies of Material Reactions by In Situ High-Resolution Electron Microscopy

MRS Bulletin ◽  
1994 ◽  
Vol 19 (6) ◽  
pp. 26-31 ◽  
Author(s):  
Robert Sinclair
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
High Resolution Electron Microscopy ◽  
Atomic Scale ◽  
Ex Situ ◽  
New Materials ◽  
Kinetic Measurements ◽  
Transmission Electron ◽  
Resolution Electron

Processing has always been a key component in the development of new materials. Basic scientific understanding of the reactions and transformations that occur has obvious importance in guiding progress. Invaluable insight can be provided by observing the changes during processing, especially at high magnification by in situ microscopy. Now that this can be achieved at the atomic level by using high-resolution electron microscopy (HREM), atomic behavior can be seen directly. Accordingly, many deductions concerning reactions in materials at the atomic scale are possible.The purpose of this article is to illustrate the level reached by in situ HREM. The essential procedure is to form a high-resolution image of a standard transmission electron microscope (TEM) sample and then to alter the structure by some means in a controlled manner, such as by heating. Continual recording on videotape allows subsequent detailed analysis of the behavior, even on a frame-by-frame (1/30 second) basis. The most obvious advantage is to follow the atomic rearrangements directly in real time. However, in addition, by continuous recording no stages in a reaction are missed, which can often occur in a series of conventional ex situ annealed samples because of the limited number of samples that can realistically be examined by HREM. One can be sure that the same reaction, in the same area, is being studied. Furthermore, by changing the temperature systematically, extremely precise kinetic measurements can be made (e.g., for activation energies and kinetic laws) and the whole extent of a material transformation can be investigated in one sample, something that would take months of work if studied conventionally. The information provided by in situ HREM is often unique and so it can become an important technique for fundamental materials investigations.

Ti-Modified Niobium-Silicide Based Directionally Solidified in-situ Composites

1996 ◽  
Vol 460 ◽  
Author(s):  
B. P. Bewlay ◽  
M. R. Jackson ◽  
H. A. Lipsitt
Keyword(s):  
Solid Solution ◽  
Fracture Toughness ◽  
High Temperature ◽  
Cold Crucible ◽  
Directionally Solidified ◽  
In Situ Composites ◽  
Czochralski Crystal Growth ◽  
Three Phase ◽  
Binary Eutectic

ABSTRACTThis paper examines microstructure-property relationships in high-temperature directionally solidified (DS) in-situ composites based on Nb silicides, such as Nb3Si and Nb5Si3. These in-situ composites are based on the Nb3Si-Nb binary eutectic, and are alloyed with Ti. They were prepared using cold crucible Czochralski crystal growth. Ternary Nb-Ti-Si alloys with Ti concentrations from 9 to 45%, and Si concentrations from 10 to 25%, were directionally solidified to generate aligned two- and three-phase composites containing a Nb solid solution with Nb3Si and Nb5Si3 silicides. Fracture toughness values generally greater than 10 MPa√m were measured in these composites. For a given Si concentration, the fracture toughness of the Ti-containing composites was increased ∼ 6 MPa√m over that of the binary alloy composites. The effects of Si concentration, and a range of Nb:Ti ratios, on microstructure, phase equilibria, and fracture toughness were examined.

scholarly journals TEM study of precipitation in a Nial-3Ti-0.5Hf single-crystal alloy

1996 ◽  
Vol 54 ◽  
pp. 998-999
Author(s):  
A. Garg ◽  
R. D. Noebe ◽  
J. M. Howe ◽  
A. W. Wilson ◽  
V. Levit
Keyword(s):  
Electron Microscopy ◽  
Heat Treatment ◽  
Transmission Electron Microscopy ◽  
Single Crystal ◽  
Argon Atmosphere ◽  
Second Phase ◽  
Directionally Solidified ◽  
X Ray ◽  
Transmission Electron ◽  
Heat Treated

Three directionally solidified NiAl single-crystal alloys, NiAl-3Ti, NiAl-0.5Hf and NiAl-3Ti-0.5Hf (at.%), were grown by a Bridgeman technique using high purity alumina crucibles. The ingots were homogenized for 32h at 1644 K followed by aging for 6h at 1255 K and finally furnace cooled under an argon atmosphere. This heat treatment was found to be very effective in dissolving Hf-rich interdendritic particles that were present in the as-cast structure, and at the same time it produced fine second-phase precipitates in the alloy.Samples for transmission electron microscopy (TEM) were prepared from 3 mm diameter cylinders electro-discharge machined from the heat-treated ingots. Slices sectioned from the cylinders were mechanically ground and electrochemically thinned in a twin-jet Tenupol-3 polisher. Microstructural and energy-dispersive X-ray spectroscopy (EDXS) studies were conducted in a Philips 400T TEM equipped with a double tilt goniometer and a KEVEX Si/Li X-ray detector.

Early Instability Phenomena of IN792 DS Superalloy

2016 ◽  
Vol 879 ◽  
pp. 2026-2031 ◽  
Author(s):  
Roberto Montanari ◽  
Oriana Tassa ◽  
Alessandra Varone
Keyword(s):  
Electron Microscopy ◽  
Dynamic Modulus ◽  
Room Temperature ◽  
Average Distance ◽  
Directionally Solidified ◽  
X Ray Diffraction ◽  
Mechanical Spectroscopy ◽  
X Ray ◽  
Microstructure Stability ◽  
Transmission Electron

Microstructure stability of the directionally solidified Ni base IN792 superalloy has been investigated by Mechanical Spectroscopy (MS), i.e. internal friction (IF) and dynamic modulus measurements. Repeated IF test runs from room temperature to 1173 K have been carried out on the same samples and a Q-1 maximum has been always observed above 700 K. Its position does not depend on the resonance frequency. After each run the values of modulus and Q-1 at room temperature change indicating that a progressive irreversible transformation occurs. Damping phenomena have been attributed to the rearrangement of dislocation structures in disordered matrix which modifies dislocation density and average distance of pinning points. The results are supported by X-ray diffraction (XRD) and transmission electron microscopy (TEM) observations.

Sign in / Sign up

Export Citation Format

Share Document